There are many known machines and methods known for making bags and pouches. Intermittent motions machines are often used to make some pouches, such as those used in the medical field. Typically such medical pouches are made from a laminate film. Laminate film, as used herein, includes a film made up of two or more layers, such as an upper layer that is sealed in various locations to a lower layer. The layers can be comprised of different materials.
Generally, the prior art provides for intermittently advancing the laminate film. When the film is stationary, a sealing platen is lowered into contact with the film. Through a combination of pressure, temperature and time, an upper layer of the laminate is sealed to a lower layer. The platen typically includes a sealing pattern for making more than one pouch. The platen is raised after the seal is formed, and the film is advanced. A downstream cutting section cuts the film into individual pouches.
Given the nature of the medical industry and the type of items being packaged, medical pouches are often made with strict tolerances. Prior art U.S. Pat. No. 6,452,354 (hereby incorporated by reference) attempted to teach how to make pouches adequate for the medical field. Generally, it taught to use a single servo motor to drive the sealing platen, and to use a force transducer to measure the force exerted by the platen. The force was used as feedback to control the servo motor. U.S. Pat. No. 6,452,354 used the force feedback to purportedly account for process variations such as properties of the material used, wear of a rubber backing surface, etc.
However, because this prior art patent uses force as its main control parameter, it requires an add-on force transducer and cannot rely on already available servo motor feedback, which adds cost and complexity. Also, it teaches the use of a single servo motor, which can result in an unbalanced platen (i.e., more force on one side than the other), and does not provide for a calibration. Moreover, it is primarily concerned with applying sufficient force and does not recognize that the force should be controlled at the upper end to prevent fracturing of the laminate film. Rather, it teaches to control excess force merely with a safety relay to prevent damage to the machine.
Accordingly, a pouch machine with multiple servo motors to control the sealing platen, and/or one that includes a calibration routine, and/or one that does not use force feedback, and/or one that prevents fracturing of the film laminate is desirable.